String groupId = model.getGroupId();
        if (groupId == null && model.getParent() != null) {
            groupId = model.getParent().getGroupId();
        }
        return groupId;
    }

    private String getVersion(Model model) {
        String version = model.getVersion();
        if (version == null && model.getParent() != null) {
            version = model.getParent().getVersion();
        }

     * used by plugins.
     *
     * @param artifacts The set of artifacts, may be {@code null}.
     */
    public void setResolvedArtifacts(Set<Artifact> artifacts) {
        this.resolvedArtifacts = (artifacts != null) ? artifacts : Collections.<Artifact>emptySet();
        this.artifacts = null;
        this.artifactMap = null;
    }

    /**

                .findFirst()
                .orElse(null);
        assertNotNull(plugin, "Unable to find plugin with artifactId: " + artifactId);
        List<PluginExecution> pluginExecutions = plugin.getExecutions();
        PluginExecution pluginExecution = pluginExecutions.stream()
                .filter(pe -> pe.getId().equals(expectedId))
                .findFirst()
                .orElse(null);

                MavenProject project = request.getProject();

                List<ModelProblem> modelProblems = null;
                Throwable error = null;

                if (project == null) {
                    project = new MavenProject();
                    project.setFile(pomFile != null ? pomFile.toFile() : null);

                    ModelBuildingListener listener =

                        prefix + prefix2 + "(groupId:artifactId)",
                        null,
                        "groupId of a plugin must be defined. ",
                        plugin);
            }

            if (plugin.getArtifactId() == null
                    || (plugin.getArtifactId() != null
                            && plugin.getArtifactId().trim().isEmpty())) {
                addViolation(